This invention relates to a device used to create independently retrievable subsea Christmas trees and subsea tubing hangers for wellheads. Subsea wellheads are typically completed using one of two configurations. In one type of completion, a tree is connected to the wellhead using a tree running tool and a tubing hanger is connected to the tree using a tubing hanger running tool.
Alternatively, in a second type of completion, a tree can be connected to a wellhead and an internal tree cap can be connected to the tree along with a tubing hanger. A tubing hanger running tool connects with the tubing hanger.
The present invention addresses a need arising from the characteristic arrangement of a tubing hanger deployed and landed above a subsea Christmas tree, or a subsea Christmas tree deployed and landed above the tubing hanger. A need has existed for a means to deploy and retrieve a tree leaving a tubing hanger in place and alternatively a method to deploy and retrieve a tubing hanger leaving the tree in place.
The upper end of a wellhead system is closed by any one of a number of devices providing control of fluid flow and pressure entering and or leaving the well. This closing device is typically installed vertically, as a cap attached to an end of one of the wellhead""s concentric body cylinders, and which seals fluid pressure at the upper end of one or more of the body cylinders.
The basic function of a wellhead is to provide for fluid flow from or into a well. The basic flow in the pathway is that of the produced or injected fluids. This may include flow of well fluids which enter or are introduced into the annulus or spaces between the concentric tubes in a wellhead or the tubular bodies which are part of the wellhead system.
Vertical connection of fluid pathways is the most basic, typical approach. Its main advantage is that it relates well to the sequential stack up of the system components. Also, it agrees with the installation motion, which is a form of vertical displacement. However, the vertical stacking of the wellhead system may have disadvantages, such as it may require rotational orientation of the system components around the well axis if the path is not entirely between concentric numbers and may require refined alignment tuning. Horizontal, radial connection of pathways requires no such rotational orientation to the well axis but fine alignment may still be needed.
Subsea Christmas trees and subsea completion because of environmental issues and overall economics need to be retrieved leaving the tubing hanger undisturbed. The tubing hanger needs to be landed in and locked to the wellhead independent to the landing and locking of the tree.
The present invention is related to a device which has separate lock and seal retract functions for a Christmas tree and for a tubing hanger so that when deploying or retrieving a Christmas tree, the seals must be retracted without unlocking the tubing hanger from the well.
A conventional tree installation requires the tree to be pulled prior to pulling the completion. A side valve tree requires the completion be pulled prior to pulling the tree.
The present invention relates to a subsea tree tubing hanger system which has the capability to deploy or retrieve a subsea tree subsea tubing hanger or subsea completion without regard to the sequence of the retrieval or deployment.
This invention relates to an improved subsea wellhead in which the tree can be removed while leaving the tubing hanger in place, or alternatively the tubing hanger can be removed while leaving the tree in place. The structure includes a wellhead housing having a wellhead internal bore and which is adapted to be supported on a seabed. A tree having an internal tree bore, is disposed above the wellhead housing and connection means, including a fine alignment key, are provided for connecting the tree to the wellhead in alignment therewith for establishing communication between the tree internal bore and the wellhead bore. A tubing hanger is landed in the tree internal bore with a production tubing string and an annular tubing string extending downwardly therefrom. In this invention, the tree has a plurality of ports such as a radial production port for communication with the production bore and with an external production line, an annular access port for communication with an annular access line, and possibly an additional port for hydraulic connection to said internal bore or for chemical injection into the tree internal bore. In operative association with the tubing hanger are slidably movable gates which are capable of opening and closing one or more of the ports, simultaneously, and obviate the need for annular seals. The gates can also be manipulated to cause outer seals in the tubing hanger to retract so that the tree can be removed from the wellhead without damaging the outer seals. Accordingly, the tree and completion can be run and/or retrieved independently. A tubing hanger and tree running tool is adapted for use with the invention. The invention includes a process, using the slidably moveable gates for removing a tree, a production tree, or a tubing hanger from a subsea wellhead and also includes a method for retrieving a tree from a wellhead without having to remove the production tubing.